In miscible displacements encountered in enhanced oil recovery processes, the unfavorable viscosity contrast between injected solvent and oil usually leads to viscous fingering (VF), a hydrodynamic instability which may result in a lower sweep efficiency and oil recovery. This phenomenon can be observed in a wide range of flows in subsurface porous media. This study examined a simple cyclic time‐dependent displacement rate and its effects on the onset and longer development of VF. It is found that such varying displacement rate can either stabilize or destabilize VF, depending on the cycle period, amplitude, and displacement scenarios. The most important mechanism is that such time‐dependent rate can effectively change the competition between convection (destabilizing effect) and dispersion (stabilizing effect). This is different from the widely used constant injection rate where the flow instability is actually determined by the Peclet number and mobility contrast for a given scenario. This study therefore provided a new aspect to control VF, either enhance or reduce, with low additional costs. It is therefore both scientifically and practically important for a wide range of flows in subsurface porous media. © 2017 American Institute of Chemical Engineers AIChE J, 65: 360–371, 2019

中文翻译：

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随时间变化的速率控制可混溶位移中的粘性指法和混合

在提高采油率过程中遇到的可混溶驱替中，注入的溶剂和油之间不利的粘度对比通常会导致粘性指法（VF），流体动力学不稳定，从而可能导致扫油效率和采油率降低。这种现象可以在地下多孔介质中的各种流动中观察到。这项研究检查了一个简单的周期随时间变化的位移率及其对VF发作和较长发展的影响。已经发现，根据循环周期，振幅和位移情况，这种变化的位移速率可以使VF稳定或不稳定。最重要的机制是这种随时间变化的速率可以有效地改变对流（破坏作用）和分散（稳定作用）之间的竞争。这与广泛使用的恒定注入速率不同，在恒定注入速率下，流动不稳定性实际上由给定情况下的Peclet数和迁移率对比决定。因此，这项研究提供了一个新的方面来控制VF，无论增加还是减少，其附加成本都很低。因此，对于地下多孔介质中的各种流动而言，这在科学上和实践上都很重要。©2017美国化学工程师学会AIChE J，65：360–371，2019